package com.chagee.store.operation.server.utils;

/**
 * @author Lee
 * @description Base64工具类
 * @date 2024/8/13 14:11
 */
public class Base64Util {
	private static final char[] ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();
	private static final char last2byte = (char) Integer.parseInt("00000011", 2);
	private static final char last4byte = (char) Integer.parseInt("00001111", 2);
	private static final char last6byte = (char) Integer.parseInt("00111111", 2);
	private static final char lead6byte = (char) Integer.parseInt("11111100", 2);
	private static final char lead4byte = (char) Integer.parseInt("11110000", 2);
	private static final char lead2byte = (char) Integer.parseInt("11000000", 2);
	private static final char[] encodeTable = new char[]{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
	private static int[] toInt = new int[128];

	public static String encode(byte[] from) {
		StringBuilder to = new StringBuilder((int) ((double) from.length * 1.34D) + 3);
		int num = 0;
		char currentByte = 0;

		int i;
		for (i = 0; i < from.length; ++i) {
			for (num %= 8; num < 8; num += 6) {
				switch (num) {
					case 0:
						currentByte = (char) (from[i] & lead6byte);
						currentByte = (char) (currentByte >>> 2);
					case 1:
					case 3:
					case 5:
					default:
						break;
					case 2:
						currentByte = (char) (from[i] & last6byte);
						break;
					case 4:
						currentByte = (char) (from[i] & last4byte);
						currentByte = (char) (currentByte << 2);
						if (i + 1 < from.length) {
							currentByte = (char) (currentByte | (from[i + 1] & lead2byte) >>> 6);
						}
						break;
					case 6:
						currentByte = (char) (from[i] & last2byte);
						currentByte = (char) (currentByte << 4);
						if (i + 1 < from.length) {
							currentByte = (char) (currentByte | (from[i + 1] & lead4byte) >>> 4);
						}
				}

				to.append(encodeTable[currentByte]);
			}
		}

		if (to.length() % 4 != 0) {
			for (i = 4 - to.length() % 4; i > 0; --i) {
				to.append("=");
			}
		}

		return to.toString();
	}

	public static byte[] decode(String s) {
		int delta = s.endsWith("==") ? 2 : (s.endsWith("=") ? 1 : 0);
		byte[] buffer = new byte[s.length() * 3 / 4 - delta];
		int mask = 255;
		int index = 0;

		for (int i = 0; i < s.length(); i += 4) {
			int c0 = toInt[s.charAt(i)];
			int c1 = toInt[s.charAt(i + 1)];
			buffer[index++] = (byte) ((c0 << 2 | c1 >> 4) & mask);
			if (index >= buffer.length) {
				return buffer;
			}

			int c2 = toInt[s.charAt(i + 2)];
			buffer[index++] = (byte) ((c1 << 4 | c2 >> 2) & mask);
			if (index >= buffer.length) {
				return buffer;
			}

			int c3 = toInt[s.charAt(i + 3)];
			buffer[index++] = (byte) ((c2 << 6 | c3) & mask);
		}

		return buffer;
	}

	static {
		for (int i = 0; i < ALPHABET.length; toInt[ALPHABET[i]] = i++) {
		}

	}
}
